Question

Which of these statements about the Patankar’s under-relaxation is true?

(a) The value form the previous iteration is modified

(b) The diagonal coefficients are modified

(c) The whole equation is modified

(d) The neighbouring coefficient is modified

I have been asked this question in an internship interview.

The doubt is from Under-Relaxation in section Discretization of the Source Term & Relaxation of Computational Fluid Dynamics

Answer 1

The correct option is (b) The diagonal coefficients are modified

To explain: Patankar’s under-relaxation modifies the value from the previous iteration, the diagonal coefficients and the neighbouring coefficients. The whole equation remains unmodified.